1. Field of the Invention
The invention relates to a friction clutch arrangement, in particular for motor vehicles, radially a clutch housing which can be fixed to a flywheel and can rotate about an axis of rotation; at least one pressure plate which is fixed against rotation with respect to the clutch housing and can move axially with respect to the clutch housing; at least one clutch disk which can be fixed against rotation with respect to a shaft, can rotate with respect to the clutch housing, and can engage a respective at least one pressure plate to transmit torque from said clutch housing to the shaft; and a clutch spring arranged on the clutch housing and loading the at least one pressure plate axially toward the flywheel with a pressing force via a first force action point. A disengagement device includes a sliding sleeve mounted concentrically on the shaft, and a first disengagement ring arranged on the sliding sleeve and operatively connected to the clutch spring at a second force action point. The sliding sleeve is axially displaceable on the shaft to introduce a disengagement force to the clutch spring via the second force action point, thereby producing a characteristic curve of disengagement force versus disengagement travel of the sleeve.
2. Description of the Related Art
Friction clutches for motor vehicles are generally known and can be constructed as a pulled or pushed clutch, the pressing force being produced by means of a spring store, for example a diaphragm spring, helical spring or disk spring. In the case of diaphragm springs, there is a special feature that their force-travel characteristic curve has a maximum, which is passed when a clutch is actuated and which, for a driver, results in an undesired alternating load.
The factors of a manually actuated vehicle clutch that determine the driving comfort for a driver and the driving behavior of a vehicle are, firstly, the value of the maximum disengagement force to be applied by the vehicle driver and, secondly, the possible maximum pressure plate disengagement stroke during a disengagement operation, which represents a measure of the separating ability of the clutch. A clutch is usually designed in such a way that the actuating force is not excessively high for an average driver and at the same time, however, secure engagement and disengagement operations can be carried out by him. Incomplete separation of the clutch produces dragging torque on the transmission input shaft, which has a detrimental effect on a subsequent shifting operation. This results in disadvantageous consequences for the lifetime of the system components, in particular the lifetime of the coupling brake in systems with unsynchronized transmissions and of the synchronizing device in synchronous transmissions being reduced.
From the prior art, it is already in principle known that an increase in the pressure plate disengagement stroke proves to be beneficial both for efficient disengagement and for a reduction in the dragging torque when the clutch is actuated.
In the conception of a clutch, with regard to the desired disengagement force and the maximum pressure plate stroke, the problem arises that, as the disengagement force is reduced, the pressure plate disengagement stroke is likewise reduced. On the other hand, if the pressure plate disengagement stroke is increased, the disengagement force is likewise increased. By contrast, however, the smallest possible disengagement force with, at the same time, a long disengagement stroke would be desirable for a vehicle driver during clutch actuation.